1. Field of the Invention
This invention relates to an aldehyde gas absorbent and a process for absorbing an aldehyde gas.
The process according to the present invention pertains to a process for adding an aldehyde gas absorbent to fiber, paper, a molding resin or a coating composition, thereby imparting thereto aldehyde gas absorbing power.
2. Description of the Related Art
In recent years, there is a rapidly increasing demand for deodorization. Among offensive odors to be deodorized, that of cigarettes have been regarded as a particularly serious problem. The odor of cigarettes is mainly composed of acetaldehyde, nicotine, pyridine and acetic acid gas.
There has been an attempt to impart deodorizing properties to various furnishings such as curtains, wall paper and the like for a house, hospital or the like and to fiber utilized for the air conditioner of an automobile, filter of electric appliances, clothes or the like.
It has been known that amine compounds have high affinity with an aldehyde gas so that an aldehyde gas in an exhaust gas can be removed by bringing the aldehyde-gas-containing exhaust gas into contact with a solution having an amine compound dissolved therein (JP-A-51-44587 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d). The amine compound in the liquid form is however not suitable for use in the daily necessaries.
A gas absorbent having an amine compound carried on a heat resistant inorganic substance has been known and it is resistant to heating treatment suffered upon addition of it to a resin, paper or a film.
For example, known are a gas absorbent having an ammonium salt, aniline or the like carried on activated carbon (JP-A-53-29292, JP-A-56-53744); an absorbent having a compound, which contains in a molecule thereof a primary amino group, carried on a magnesium silicate clay mineral (JP-A-9-28778); and an absorbent having a polyamine compound carried between layers of a layered phosphate (xcex1-zirconium phosphate) (Tsubafuru, et al., PHARM. TECH. JAPAN, 12, 12, 77-87(1996)).
In addition, known are a carbon dioxide gas absorbent having an amino alcohol carried on silica (JP-B-53-23899); a deodorizer having a polyallylamine carried on silica (JP-B-63-141642); and a carbon dioxide gas absorbent having both water and an amine compound, which has a molecular weight per N atom of 110 or less and a boiling point of at least 100xc2x0 C., carried on silica gel (JP-B-4-200742). However, it is hardly considered that these gas absorbents have aldehyde gas-absorbing power sufficiently satisfying requirements at an industrially level.
The gas absorbent employing activated carbon as a carrier is not usable in the sanitation-related fields because coloring occurs when it is kneaded into a resin or fiber.
An object of the present invention is to provide an aldehyde gas absorbent which has a specific polyamine compound carried on a specific porous silicon dioxide to have an improved aldehyde gas-absorbing power.
Another object of the present invention is to provide a process for absorbing an aldehyde gas using the aldehyde gas absorbent.
A still other object of the present invention is to provide an aldehyde gas absorbing article comprising the aldehyde gas absorbent.
Other objects and effects of the invention will become more apparent from the following description.
The above-described objects of the present invention have been achieved by providing the following absorbent, process and article:
An aldehyde gas absorbent comprising:
a porous silicon dioxide having a specific surface area of from 400 to 900 m2/g and an average pore size of from 0.1 to 10 nm; and
a polyamine compound carried on the porous silicon dioxide in an amount of from 0.02 to 2.0 mmol/g, said polyamine compound being represented by the following formula:
H2Nxe2x80x94(CH2CH2xe2x80x94NH)nxe2x80x94CH2CH2NH2
wherein n stands for an integer of from 0 to 3;
A process for absorbing an aldehyde gas, which comprises incorporating an aldehyde gas absorbent as defined above in a medium; and
An aldehyde gas-absorbing article comprising a medium and an aldehyde gas absorbent as defined above.
The aldehyde gas absorbent (which will hereinafter be abbreviated as xe2x80x9cabsorbentxe2x80x9d) according to the present invention has a polyamine compound carried on the specific silicon dioxide described below. The amount of the polyamine compound carried on the silicon dioxide is 0.02 to 2 mmol, preferably from 0.2 to 1.1 mmol, per gram of the absorbent. When the amount is too small, the aldehyde gas absorbing power lowers. When the amount is too large, on the other hand, not only the polyamine compound becomes a cause for coloration, coming out from the silicon oxide by heating upon kneading with a resin or fiber but also the polyamine compound itself becomes an offensive odor, which reduces the absorption amount of an aldehyde gas. The amount of the polyamine compound carried on the silicon dioxide can be easily calculated from the nitrogen content detected by organic element analysis.
The absorbent according to the present invention preferably has an elution amount of the polyamine compound in terms of a nitrogen concentration, as measured by the following testing method, of 1 ppm or less.
(Testing Method)
In a polyethylene bottle, 1 g of a sample and 100 ml of pure water are charged, followed by shaking at 40xc2x0 C. for 60 hours. The contents in the polyethylene bottle are filtered and the nitrogen concentration of the filtrate is measured.
The absorbent having less elution amount of a polyamine compound is excellent in the aldehyde gas absorbing power and heat discoloration resistance.
The absorbent according to the present invention is usually obtained in powdery form and it preferably has an average particle size of from 0.01 to 50 xcexcm, more preferably from 0.1 to 20 xcexcm, still more preferably from 0.1 to 5 xcexcm. Absorbents having an average particle size less than 0.01 xcexcm are not preferred, because it is accompanied with such problems as difficulty in handling and tendency to re-coagulation. Absorbents having an average particle size greater than 50 xcexcm, on the other hand, are not preferred, because it is accompanied with such problems as difficulty in uniform dispersion in a resin and occurrence of yarn breakage upon spinning.
The absorbent of the present invention is effective for the absorption of an aldehyde gas. Examples of the aldehyde gas include acetaldehyde, formaldehyde, nonenal, crotonaldehyde and aryl aldehydes.
Silicon Dioxide
The silicon dioxide for use in the present invention is a porous silicon dioxide having a specific surface area of from 400 to 900 m2/g and an average pore size of from 0.1 to 10 nm. It preferably has a specific surface area of from 500 to 900 m2/g and an average pore size of from 2 to 8 nm.
Excessively small specific surface areas reduce the contact area of the polyamine compound with an aldehyde gas, thereby decreasing the gas absorption amount. Excessively large specific surface areas, on the other hand, tend to cause heat discoloration upon addition and kneading of a resin. The specific surface area can easily be determined by calculating the nitrogen absorption amount in accordance with the BET method.
Excessively large average pore sizes of the porous silicon dioxide bring about a reduction in the specific surface area, which lowers the amount of the polyamine compound carried thereon, thereby deteriorating the aldehyde gas absorption capacity. When the specific surface area is adjusted to a satisfactory size in spite of a too large average pore size, the void in the porous body becomes excessively large, which causes a deterioration in the mechanical strength or lowers the carrying capacity of the polyamine compound, resulting in the problem that the silicon dioxide inevitably releases the polyamine compound even by slight heating. When the average pore size is too small, on the other hand, the specific surface area of the silicon dioxide increases, but the polyamine compound cannot enter the pore easily, which makes it impossible to increase the carrying amount of the polyamine compound, leading to a decrease in the gas absorption capacity. The average pore size (D) can be calculated easily from the equation shown below, with using the pore volume and specific surface area determined by the BET method.
D=4xc3x97V/Scxc3x97104
wherein
V: pore volume (ml/g), and
Sc: specific surface area (m2/g)
The preferred water content of the silicon dioxide of the present invention is from 0.1 to 10 wt. %, more preferably from 0.1 to 5 wt. %.
At a water content less than 0.1 wt. %, the silicon dioxide does not have a sufficient amount of silanol groups on its surface and therefore, its carrying capacity of the polyamine compound of the present invention is small. At a water content greater than 10 wt. %, on the other hand, the silicon dioxide becomes a cause for coloration, foaming or deterioration upon kneading with a resin.
The porous silicon dioxide can be dried, for example, by heating or pressure reduction. Either one can be employed.
Although the drying degree may be adjusted as needed, it is general that the larger the amount of the amine compound to be carried on the porous silicon dioxide is, the more the drying degree is heightened.
The water content of the porous silicon dioxide can be measured easily by the thermogravimetric analysis.
For example, the water content can be easily calculated, as a ratio of the heating loss to the weight of the silicon dioxide before heating, by heating the porous silicon dioxide at a rate of 10xc2x0 C./min from room temperature to 500xc2x0 C. and then measuring the heating loss by using a differential thermogravimeter (xe2x80x9cModel TG-DTA220xe2x80x9d, trade name; manufactured by Seiko Instruments Inc.).
Polyamine Compound
The polyamine compound for use in the present invention contains in the molecule thereof a primary amino group and is represented by the following formula:
H2Nxe2x80x94(CH2CH2xe2x80x94NH)nxe2x80x94CH2CH2NH2
wherein n stands for an integer of from 0 to 3 and is preferably 1 or 2.
The above-described polyamine compound is in liquid form at room temperature, has high decomposition and boiling points and contains a primary amino group, which has high reactivity with an aldehyde gas.
Preparation Process of the Absorbent
The absorbent according to the present invention is easily obtained by mixing the above-described silicon dioxide and polyamine compound.
The polyamine compound can be carried on the silicon dioxide uniformly by diluting the polyamine compound with water or the like and then mixing it with the silicon dioxide. In general, an excess amount of the polyamine compound is mixed with the silicon dioxide. Therefore, the resulting substance is then washed with pure water to remove the excessive polyamine compound adhered onto the surface of the silicon dioxide. The washed substance is then dried at 50 to 120xc2x0 C., to thereby obtain the absorbent according to the present invention.
For preparing the absorbent of the present invention, the following process is particularly preferred. Specifically, after the water content of the porous silicon dioxide, which has a specific surface area of from 400 to 900 m2/g and an average pore size of from 0.1 to 10 nm, is adjusted to 0.1 to 10 wt. %, the polyamine compound of the present invention is carried thereon in an amount of 0.02 to 2.0 mmol/g.
The above-described process does not need a washing step so that an amine effluent which may cause environmental pollution is not discharged and in addition, a drying step after washing is not required, which makes it possible to easily prepare an absorbent having high aldehyde removing properties and heat discoloration resistance.
The process is characterized by the use of porous silicon dioxide having a specific water content as a carrier of the polyamine compound. Compared with the ordinarily employed porous silicon dioxide having a water content not less than several tens wt. %, the porous silicon dioxide used in the preferred process of the present invention has been dried highly. The water content is preferably from 0.1 to 5 wt. %, more preferably from 0.1 to 2 wt. %, particularly preferably from 0.1 to 1 wt. %.
In order to easily prepare an absorbent which does not elute the polyamine compound much, it is effective to adjust the water content of the porous silicon dioxide to from 0.1 to 10 wt. % and then allow the polyamine compound to be carried thereon in an amount of from 0.02 to 2.0 mmol/g.
Although there is no particular limitation imposed on the timing to allow the polyamine compound to be carried on the porous silicon dioxide, it is generally preferred to perform the carrying step immediately after the drying step during the preparation of the porous silicon dioxide or immediately after the drying step after the preparation of the porous silicon dioxide. An absorbent excellent in heat discoloration resistance can be obtained by allowing the polyamine compound to be carried immediately after the drying step of the porous silicon dioxide.
Mixing of the polyamine compound with the porous silicon dioxide or pulverization of the resulting mixture can be effected using an ordinarily-employed mixer such as Henschel mixer, oscillating mill or ball mill. It is also possible to classify the absorbent as needed by a commonly employed classifier such as vibration sieve or cyclone.
Applications of the Absorbent
The absorbent according to the present invention is substantially free from deterioration such as lowering in the aldehyde gas absorbing power or discoloration, even when heated at 200xc2x0 C. or higher or exposed to ultraviolet rays, and thus is stable against high temperature or exposure to light.
The absorbent of the present invention is white in color and even when it is incorporated in a resin, the resin is not colored.
In addition, the absorbent of the present invention scarcely elutes the polyamine compound even when brought into contact with water.
Accordingly, the absorbent of the present invention can be formed or molded into a desired shape after incorporated in various resins or paper, without causing a problem of deterioration due to high temperature or light. Moreover, the formed or molded product is, upon storage and use, substantially free from limitations concerning heating temperature or shading.
The absorbent according to the present invention can impart an article such as molded resin articles, wall paper, fiber, films, coating compositions, covering agents, floor and wall materials, building materials, paper and the like with aldehyde gas absorbing power by being incorporated therein.
The absorbent of the present invention has a reactive-type absorption mechanism so that it is effective for the applications requiring a high gas absorption rate.
Articles having incorporated therein the absorbent of the invention such as a molded resin article, wall paper, fiber, a coating composition, paper, leather, plywood and a spray agent are described below.
Molded Resin Article
The absorbent of the present invention can easily impart a molded article of a resin with an aldehyde gas absorbing power by mixing with the resin and then molding the resulting mixture. Preferred examples of the resin include polyester, nylon, acrylics, polyethylene, polypropylene, polyvinyl, polyvinylidene, polyurethane, polyvinyl chloride and polystyrene resins. Each of these resins may be either a homopolymer or a copolymer.
The absorbent of the present invention is preferably added to the resin in an amount of from 0.1 to 20 parts by weight, more preferably from 0.5 to 10 parts by weight, per 100 parts by weight of the resin.
To the resin, additives such as delustering agent, colorant, antioxidant, fluorescent brightener, stabilizer, thickener, flame retardant, antibiotic, mildewproofing agent, mothproofing agent, infrared ray absorbent or ultraviolet ray absorbent can be added in a conventional manner.
Wall Paper
There are three raw materials for wall paper, that is, paper, cloth and resin. Paper includes Japanese paper and machine-made paper. The latter is rich in color and pattern, light and easy to bond. It is classified into salbura, tekko, mica, crepe, satin, bronze and the like, depending on the surface finish. The Japanese paper is accompanied with the drawbacks such as low mechanical strength and poor stain resistance, but mechanical strength and stain resistance can be improved by processing the surface with a resin.
Cloth-made wall paper is excellent in sound absorbing qualities and heat insulating properties. Examples of the cloth used for it include silk.wool fabrics, chemical fibers, paper textile, hemp cloth, cotton cloth and glass fiber cloth. These materials are usually lined with senkashi (hand-made paper) or kraft paper.
It is also possible to line a polyvinyl chloride film with paper, cotton cloth, victoria lawn or the like and impart it with appearance of some material by embossing or printing. The resulting film is poor in air permeability but rich in waterproofness so that it can be used in a bath room, lavatory and the like. A laminate film prepared by printing grain patterns or textile patterns on the surface of paper and then laminating thereon a clear polyvinyl chloride film can be used widely for the decoration of the interiors of houses.
Specific examples of a resin suitable as a material or laminating material of wall paper include polyvinyl chloride resin, polyethylene resin and polypropylene resin.
The above-described resin may be a copolymer as well as a homopolymer. The copolymer includes copolymers of the monomer constituting the resin and an other monomer copolymerizable therewith and graft copolymers obtained by grafting, on the monomer constituting the resin, an other monomer copolymerizable therewith.
Preferred examples of the monomer copolymerizable with vinyl chloride include xcex1-olefins such as ethylene, vinyl esters such as vinyl acetate, vinyl ethers such as butyl vinyl ether, esters of (meth)acrylic acid, aromatic vinyl compounds such as styrene, halogenated vinyls such as vinylidene chloride, and N-substituted maleimides such as N-cyclohexyl maleimide. Two ore more of these monomers may also be copolymerized. In the wall paper of the present invention, the absorbent is preferably added in an amount of from 0.01 to 30 wt. %, more preferably from 0.5 to 20 wt. %, most preferably from 1 to 15 wt. % based on the weight of deodorizing wall paper.
To wall paper having a resin layer, it is possible to add a blowing agent, processing assistant, lubricant, antifogging agent, antioxidant, ultraviolet light absorber, flame retardant, filler, colorant, stabilizer or the like to a resin component.
The deodorizing wall paper of the present invention may be obtained by allowing the above-described absorbent to be carried on a wall paper material such as paper, cloth or resin.
For example, the case where a resin is used as a base material for the deodorizing wall paper is described below.
Such wall paper can be obtained by adding the absorbent of the present invention to a base material resin, kneading the resulting mixture in a roll mill, forming the kneaded mass into a sheet on the surface of a releasing material by calendering and releasing the sheet from the releasing material; or rolling and calendering the base material resin, applying thereto an absorbent having a binder incorporated therein and then drying.
There is no particular limitation imposed on the method of attaching the wall paper. Direct adhesion, facing after lining or any other method can be employed for the attachment.
The deodorizing wall paper according to the present invention is excellent in deodorization of volatile smelly substances such as formaldehyde emitted from building materials such as wall board. The discoloration or deterioration of deodorizing properties does not occur even by heating it.
Coating Composition
A coating composition generally contains film-forming components such as main film component, plasticizer, curing agent, emulsifying agent, dispersant and pigment which is added as needed, and a film-forming assistant component including a solvent, diluent and the like.
As the main film component in the present invention, any one of natural vegetable oils, natural resins, semi-synthetic resins and synthetic resins can be used. Alternatively, either a thermoplastic resin or thermosetting resin can be employed.
Specific examples of the fat or oil include drying oils such as linseed oil and semidrying oils, while those of the resin include rosins, ethyl cellulose, cellulose acetate butyrate, benzyl cellulose, novolak or resol type phenol resins, alkyd resins, aminoalkyd resins, acrylic resins, polyvinyl chloride, silicone resins, homopolymer type thermoplastic, copolymer type thermoplastic, modified type thermoplastic or thermosetting fluorine resins, epoxy resins, urethane resins, saturated polyester resins, melamine resins and polyvinylidene chloride resins.
The coating composition of the present invention is in the liquid form. Either a solution or dispersion may be used. As a solvent, any one of lipophilic organic solvents, hydrophilic organic solvents and water can be used.
The coating composition of the present invention may be set by any mechanism. Specific examples of the setting mechanism include oxidative polymerization, humidity setting, thermosetting, catalytic setting, ultraviolet-light setting and polyol setting.
Preparation Process of Coating Composition
The coating composition of the present invention can be easily obtained by mixing the above-described absorbent and coating components in a conventional manner by using an ordinarily employed mixer such as ball mill.
The absorbent is preferably added to the liquid coating composition of the present invention in an amount capable of imparting the resulting film with aldehyde gas absorbing effects without damaging the properties of the coating composition, more specifically, in an amount of from 0.1 to 10 wt. % (xe2x80x9cwt. %xe2x80x9d will hereinafter be abbreviated as xe2x80x9c%xe2x80x9d) based on the solid content of the coating composition. If it is desired to use the resin, which is contained the liquid coating composition of the present invention, as a binder for the absorbent and allow a large amount of the absorbent to adhere to a target substance, thereby permitting the target substance to exhibit aldehyde gas absorbing properties, the absorbent is preferably added in an amount of from 10 to 60% based on the solid content of the coating composition. It is possible to increase the amount of the absorbent as needed for the long lasting exhibition or quick exhibition of the aldehyde gas absorbing effects.
Applications and Setting Method
There is no particular limitation imposed on the method of applying the coating composition of the present invention. Depending on the properties of the coating composition, an appropriate method is selected from brushing, spray coating, dip coating or the like.
No particular limitation is imposed on the setting method of the coating composition of the present invention and any one of cold setting, heating and exposure to ultraviolet rays, visible light, electron beams or the like can be employed.
Scope of Application
Examples of the objects to which the coating composition is applied include: buildings such as hospitals, schools, houses, food plants; transportation means such as automobiles, airplanes and railway vehicles; interior finishes of a house such as walls, ceilings and floors of a bathroom, lavatory or kitchen; and electric appliances such as refrigerator and microwave oven. The coated film formed by applying the coating composition of the present invention to the surface of such an object is able to absorb offensive odors such as acetaldehyde which is a cause for the smell of cigarettes or formaldehyde smell emitted from wall paper or the like.
The coated film formed by the application of the coating composition of the present invention exhibits excellent absorbing properties against an aldehyde gas without damaging its weather resistance.
Deodorizing Fiber
The deodorizing fiber of the present invention have the above-described absorbent incorporated in fiber.
As the fiber, either natural fibers or synthetic fibers and any one of short fibers, long fibers and composite fibers having a core-sheath structure can be employed.
Since the absorbent of the present invention has excellent heat resistance, deodorizing properties of it are not deactivated even when it is exposed to high temperature up to 200xc2x0 C. at the stage of adding the absorbent to a fiber resin. It is therefore possible to use any resin conventionally used as a fiber resin.
Preferred examples of the natural fiber include pulp, hemp, cotton, silk and wool, while those of the synthetic fiber include polyester, nylon, acrylics, polyethylene, polyvinyl alcohol, polyvinylidene, polyurethane and polystyrene. As a resin for the synthetic fiber, either a homopolymer or a copolymer may be employed.
No particular limitation is imposed on the incorporating method of the absorbent in the fiber. It is incorporated, for example, by melt spinning, dry spinning or wet spinning of a fiber resin which has the absorbent incorporated therein in advance; or by allowing an aqueous or organic suspension containing the absorbent and a binder to adhere on the surface of the fiber by coating, dipping or the like method and then removing the solvent. In order to improve the dispersibility of the absorbent, a surfactant, a dispersant or the like can be added to the above-described aqueous or organic suspension. Any one of anionic, nonionic and cationic surfactants can be employed as the surfactant. As the binder for heightening the adhesion to the fiber surface, any binder can be employed without limitation insofar as adhesion is exhibited after the removal of the solvent.
The absorbent is preferably incorporated in the fiber in an amount of from 0.1 to 20 parts by weight (xe2x80x9cparts by weightxe2x80x9d will hereinafter be abbreviated as xe2x80x9cpartsxe2x80x9d), more preferably from 0.5 to 10 parts based on 100 parts of the natural fiber or synthetic fiber resin.
It is possible to add as needed, to the fiber, various additives such as gas decomposer, delustering agent, colorant, antioxidant, fluorescent brightener, stabilizer, flame retardant, antibiotic, mildewproofing agent, aromatic, mothproofing agent, infrared light absorber and ultraviolet light absorber.
Applications of the Deodorizing Fiber
The deodorizing fiber of the present invention can be used for a large number of fiber products such as underwear, socks, comforters, carpets, curtains, masks, handkerchiefs, hats, paper, nonwoven clothes and towels.
The deodorizing fibers according to the present invention can be used as raw materials for various deodorizing fiber products such as composite fibers, woven clothes and nonwoven clothes.
Paper
The paper for use in the present invention includes a natural pulp and a synthetic pulp. Preferred examples of the natural pulp include wood pulp, while preferred examples of the synthetic pulp include polypropylene, polyethylene, alumina fibers, carbon fibers and glass fibers.
The aldehyde gas absorbent can be easily incorporated in the paper by a known method such as paper manufacturing, coating, dipping or spraying.
The amount of the absorbent to be incorporated in the paper is preferably from 1 to 20 wt. %.
The paper containing the aldehyde gas absorbent is useful as, for example, a sanitary pad, packaging paper, paper for transportation or a corrugated board.
Leather
Preferred examples of the leather for use in the present invention include cowhide, sheepskin, pigskin, horsehide, kangaroo skin and goat skin. Leathers manufactured by any method can be used in the present invention.
The absorbent of the present invention may be incorporated in the leather by a known method, such as adhering the absorbent to the leather with a binder, or impregnating the leather with a liquid having the absorbent dispersed therein.
The amount of the absorbent to be incorporated in the leather is preferably from 1 to 20 wt. %.
Plywood
The plywood for use in the present invention preferably comprises veneers, which are bonded to each other and each of which is made of wood such as cedar, pine or lauan. The absorbent according to the present invention may be incorporated in the plywood by a known method, such as adhering the absorbent to the plywood with a binder, or impregnating the plywood with a liquid having the absorbent dispersed therein.
The amount of the absorbent to be incorporated in the plywood is preferably from 1 to 20 wt. %.
Spray Agent
A spray agent can be obtained by dispersing the absorbent according to the present invention uniformly in a volatile liquid. Preferred examples of the volatile liquid include known hydrocarbon liquids such as isobutane.
The amount of the absorbent to be incorporated in the volatile liquid is preferably from 1 to 20 wt. %.